Pointing to a photograph,a man said,"$I$ have no brother or sister,but that man's father is my father's son." Whose photograph was it?

$A$ family consists of six members $P, Q, R, X, Y,$ and $Z$. $Q$ is the son of $R$ but $R$ is not the mother of $Q$. $P$ and $R$ are a married couple. $Y$ is the brother of $R$. $X$ is the daughter of $P$. $Z$ is the brother of $P$. How is $Q$ related to $X$?

Pointing to a man on the stage,Rita said,"He is the brother of the daughter of the wife of my husband." How is the man on the stage related to Rita?

$A$ is the son of $B$; $C$,$B$'s sister,has a son $D$ and a daughter $E$; $F$ is the maternal uncle of $D$. How is $F$ related to $E$?

Pointing to a person,a man said to a woman,"His mother is the only daughter of your father." How was the woman related to the person?

If $X$ is the brother of the son of $Y$'s son,how is $X$ related to $Y$?